class SliderCrankLinkage : public QWidget
{
    Q_OBJECT
public:
    explicit SliderCrankLinkage(QWidget *parent = nullptr);
protected:
    void paintEvent(QPaintEvent* e);
};

void SliderCrankLinkage::paintEvent(QPaintEvent *e)
{
    Q_UNUSED(e);

    QPainter pbearing(this);
    pbearing.setPen(QPen(Qt::black, 5, Qt::SolidLine, Qt::RoundCap, Qt::RoundJoin));
    QLine AB(0, 0, 60, 0), BC(0, 0, 60, 0), CA(0, 0, 60, 0);

    QTransform transform;
    transform.translate(150, 150);
    pbearing.setWorldTransform(transform);
    pbearing.drawEllipse(-40, -40, 80, 80);
    pbearing.drawEllipse(-25, -25, 50, 50);
    transform.rotate(+60.0);
    pbearing.setWorldTransform(transform);
    pbearing.drawLine(AB);
    transform.rotate(+60.0);
    pbearing.setWorldTransform(transform);
    pbearing.drawLine(BC);
    transform.rotate(-60.0);
    transform.translate(60.0, 0);
    transform.rotate(+120.0);
    pbearing.setWorldTransform(transform);
    pbearing.drawLine(CA);
    transform.translate(30.0, 0);
    pbearing.setWorldTransform(transform);
    pbearing.drawLine(50, 0, -50, 0);
    pbearing.setPen(Qt::NoPen);
    pbearing.setBrush(QBrush(Qt::black, Qt::BDiagPattern));
    pbearing.drawRect(50, 0, -100, -25);
}